Production of calcium arsenate free from water-soluble arsenic



Patented ar a, was.

JAMES RAH M LAMB, 0F DENVER, ooLoEAno, Assreuoza 'ro AMERICAN smE 'rme AND EEEIEIEG COMPANY, or NEW YORK. N. Y., A ooEroRA'rIoE or NEW JERSEY.

PRODUCTION OF CALCIUM ARSENATE FREE FIR/0M WATER-SQLUBLE ARSENIG.

Ho Drawing.

To all ,whom it may concern:

Be it known that I, J AMns GRAHAM LAMB, a citizen of the United States. and resident of Denver, in the county of Denver and State of Colorado, have invented certain new and useful Improvements in the Production of Calcium Arsenate Free from Water- Soluble Arsenic, of which the following is a specification.

The invention relates to an improved process for producing basic calcium ar senate free from water soluble arsenic.

The primary object of the invention is to provide a simple process for treating an arsenic suppl 1n material such as arsenic trioxide As In such a way that there will be produced a basic arsenate, such as calciumarsenate free from soluble arsenic.

The novelty of the process consists rimarily in treating a normal arsenate suc as trisodium arsenate, with a slight excess of caustic soda in solution with lime to precipitate insoluble basic calcium arsenate free from water soluble arsenic.

Descrlbed more in detail, the process conslsts 1n oxidizin the white arsenic, by the use of nitric aci and the resultin solution of AS2Q5 is treated with caustic so a to form a solutlon of trisodium arsenate which is a normal salt.

Application filed February 1, 1921.

Serial No. 441,684.

A basic reagent, suchas slacked lime in a suspension, is added to the alkaline solution of the trisodium arsenate, in the presence of a slight excess of caustic soda in the solution and calcium arsenate is precipltated therefrom in a finely divided granular form.

The resulting basic calcium arsenate produced by this method is insoluble and entirely free from water soluble arsenic. The

mother liquid is evaporated to a concentration of about sodium hydroxide and is used in the caustic soda solution.

Having thus described my invention, I

from" acid arsenates and adding calcium hydroxide in the form of a suspension to transfer all 6f the arsenic acid of the neutral salt into an insoluble arsenate.

Signed at Denver in the county of Denver and State of Colorado this 18th day of January A. D. 1921.

I J. GRAHAM LAMB. 

